1. Technical Field
The invention relates generally to computer graphics systems, and, more particularly, to a method and apparatus for generating pick information in computer graphics systems.
2. Description of the Related Art
An essential part of interactive graphics systems is a picking operation in which a user identifies one or more objects of a three dimensional scene for subsequent processing. Typically, the user uses a pointing device such as a mouse or light pen to position a cursor or picking window over a portion of the three dimensional scene and to make the desired selection.
Picking is described in such references as U.S. Pat. No. 4,847,605 to Callahan et al.; U.S. Pat. No. 4,870,599 to Hempel et al.; U.S. Pat. No. 5,255,359 to Ebbers et al.; and U.S. Pat. No. 5,373,514 to Lawless et al., all assigned to the assignee of the present invention.
Picking typically is performed by defining a picking aperture and traversing all the primitives of the three dimensional scene to determine those primitives that are intersected by the picking aperture. The user then may select one of the intersecting primitives as the picked object. In the alternative, the intersecting primitives may be depth sorted using conventional z-buffer techniques and the front most primitive selected as the picked object.
In a detailed three dimensional scene, traversing all of the primitives to determine those primitives intersected by the picking aperture may be very intensive, and thus make the picking operation slow.